Muted alerts are supressed and add "mutedBy" to APIv2

[grobinson-grafana]

This commit updates TimeMuteStage to mark muted alerts as suppressed, and adds the names of all mutes that mute the alert to a field called mutedBy. This field is also returned in APIv2.

Fixes #3513

[grobinson-grafana]

Should I also update apiv1? I'm not sure if that's in maintenance mode or still receiving features?

[gotjosh]

I chatted with George offline for a bit, and it turns out this doesn't do what he thought it did. It suffers from a "race" where an alert from one route can override the status from the same alert going through another way.

Because time intervals are at a route level, the filtering must show on which route was the time interval active so that underlying data structure needs to change to accommodate that requirement.

[grobinson-grafana]

I've decided to make this a draft for the time being as there is a lot of work still to do and there are still some decisions to make about how to best add this feature.

[jasuade]

Hey team! Is there any progress on this task?

thank you!

[grobinson-grafana]

I'm closing this to start over, as it's been almost 6 months since we last worked on it. There are some conflicts with main that I need to fix, and I am considering doing something a little different this time.